Stehlik



Oct. 16, 1928.

-R. F. STEHLIK TELEPHONE SYSTEM Filed May '7, 1926 8 Sheets-Sh et 1 GEE M L- Oct. 16, 1928.

R. F. STEHLIK TELEPHONE SYSTEM 8 Sheets-Sheet 2 Filed May- '7, 1926 Oct. 16, 1928.

R. F. STEHLIK TELEPHONE SYSTEM Filed May 7, 1926 8 Sheets-Sheet 4 Oct. 16,1928.

8 Sheets-Shed 5 Filed May '7, 1926 Oct' 16, 1928.

R. F. STEHLIK TELEPHONE SYSTEM File May 1926 8 Sheets-Sheet 7 nsu mmhmmm mHW m kad s. N

Oct. 16, 1928.

R. F. STEHLIKI TELEPHONE SYSTEM Filed May '7, 1926 8 Sheets-Sheet 8 E E N mmm mmm MH E "'Inuen nr fiu i l h F1 STEhhk special object or Patented Get. 16, 1928.

STrhlfiiES .Z ATEhlT RUDOLPH F. STEHLIK, OF CHICAGO, ILLINOIS, ASSIGIIOR TO AUTOIVIA'LIC ELECTRIC IIQ'CL, OF CHICAGO, ILLINOIS, A CCRPOHATIQN OF DELA'W'ARE.

TELEPHCNE SYSTEIQ.

Application rues May 7, 1826.

The present invent on relates-in general to telephone systems, bu is concerned more particularly with telephone systems of the type in which so-called finder switches or line finders are employed to connect an. idle trunk line with a calling subscribers line; and a e invention is an improvement in such '0 stems which permits the grouping of the subscribers lines into relatively large groups which are accessible through two or more interrelated groups of finder switches. I

Y In the embodiment of my IlRVQIllTlOIl, I propose to use a finder switch of the two-motion type, i. e., a switch whose wipers are moved first in a vertical direction and then in a hori- Zontal direction to the desired bank contact set. Moreover, I propose to equip the finder s vitches with a double set of wipers, and double set of banks through which the finder switch will have access to 200 lines. Moreover, I propose t use a finder switch oi the directive type, i. e-., a. switch which is directed to the bank contacts of the calling line by an external ending 'mechauism. rather than a finder of the hunting type which searches for a particularly marked contact designating the calling line. Associated with and common to a group of finder switches I provide control "dent comprising a sending mechanism,

a sec .ence switch for controlling the same,

relays for associating control equipment with the group containing the calling line, control reiavs for controlling the sender, sequence switch and register, and an allotter.

switch throu h which the control eouipment .rom the second hundred lines or B group, are handled through the wipers the second or B group of finders, which in turn are controlled by a second control. equipment. lhese two finder groups and their respective ssociated control equipments, are inter-related and inter connected so that the 200 line group of subscribers lines is served jointlyby the two serial No. 107,238.

finder groups, as will be set forth hereinafter.

. One of the objects of theinvention is to provide circuit means such that if two simultaneous calls are started in one of the one hundred line groups mentioned above, a finder switch in thefirst choice group will be con trolled by the first choice control equipmentto connect with one of the calling lines, and a finder switch in the second choice group will be controlled by a seond control equipment to connect with the other of the calling lines, the second finder being started as soon as the first control equipment has switched through provided no line in the second group is calling at the instant. 7

If two simultaneous calls are initiated in one line group at the same time that a call is initiated in the other line group, one call from each line group will be immediately hant led by the finder equipment which is first choice to that line group. The second call in the first mentioned line group will be handled by the finder control equipment which first restores to normal. I

Another object ofmy invention is to provide circuit arrangements whereby it the finder, operated in response to a calling line from the group of lines to which it is first choice, fails to connect with that lin due either to a mechanical or electrical defcctin the finder or control equipment,themechaism involved will be immediately released, and a finder in the second choice group will be controlled by the second control equipment to connect with the calling line. If the trouble is of such nature that the control equipment is prevented from restoring to normal, all subsequent calls are handled by the second control equipment, and an alarm is brought up to point out the trouble in the first control equipment.

Another object of my invention is to provide a manual key which is operated to disconnect either group ofcont-rol equipment in case that equipment is in need of adjustment or repairing, inwhichcasecalls from either group of lines are handled by either group of finder switches under the control of the one remaining group of control equipment, that is. the finders are all grouped together in one large group under the control of the one control equipment which is in working order at the time.

Another object of my. invention is to provide an all-finders busy relay in the control equipments, that relay being energized as long as an idle finder remains in the group controlled by the equipment. \Vhen the last finder in the group is seized and operated the all-finders busy relay deenergizes, and cuts the control equipment momentarily out of service so that all calls from either group of lines are handled by the other finder group and control equipment.

As a further object of my invention I pro vide separate fuses for the control e uipinent switching relay and fuse the all-finders busy relay in common with the control equipment and senders, so that in the event that the latter fuse blows, disabling the sender and control equipment, the all-finders busy relay deenergizes and the control equipment switching relay energizes to transfer subsequent calls to the other finder and control equip ment group.

In accordance with the requirements of 'established telephone practice I provide discriminating tones by means of which the toll recording operator is informed as to the classes of toll service to which the calling subscriber is entitled. In making this provision, I arrange the discriminating tone circuits so that the proper tone will be given independcnt of the finder group through which the call is handled.

A further object of my invention is to provide an in'iproved sender circuit in which a common interrupting device sends impulses sinniltaneously to the motor magnet of the finder switch and to the motor magnet of the stepping control switches of the sender, the interrupter equipment being controlled by a stepping relay which is controlled by re ertive pulses from the finder switch magnet and from the sender switch magnet. In case either the finder switch or the sender switch. magnet fails to operate properly and does not deliver its rcvertive pulse, a slow operating relay timed to operate after a definite interval, switches the call to the other group.

- As a further object of my invention I provide a new and improved circuit "for restoring the counting switches of the sender switches to normal. Heretofore such switches have been restored through the medium oi a wide wiper which bridged. the contacts over which it passed and through which the magnet circuit was closed. This wiper was subject to considerable wear, which greatly shortened the life of the switch. In improving this feature I use a return to normal relay which controls the magnets of the senders. That relay is differentially wound and when the wipers of the senders reach the next to normal contact set, a' circuit is closed through the second winding of the relay, to deencrgize it and open the magnet circuits. The sender switch magnets deenergize, advancing the wipers one step into the normal position.

vFurther objects of the invention, not specifically enun'ierated here, will be apparent from the detailed specification and claims which follow. n p

The drawings compr ng 1 to 8, inelusive, when arranged with Figs. 1, f2, and 3 in a horizontal row with Figs. 4-, 5, and 6 a second horizontal row directly l. ll(3tltll the first with. Fi 7 beneath Fig. 5, and Fig. 8 beneath Fig. 7, with all corresponding lines in alignment, show sitrliicient circuit details to enable a clear understanding of the invention. Vith the drawings so arranged the equip ment shown in Figs. 3 and 6 and on the right hand side of Figs. 5, 7, and 8 comprises finch er and control equipment group which will be hereinafter designated as group A; and the equi mient shown in. F f l and fit, and on the lett hand side of Figs. 5, 7, and 8 comprises a group of finders and control equipment hereinafter designated as group B. 2 shows the line equipment of a 200 line-group of subscribers lines, those lines being seized by the finders in either group A or group P. However, the normal running of the system the lines A and A etc., in the 100 line-group that is, numbers from to 199, inclusive,

will be seized by finders in groi'ip A, those finders being the first choice of that group of lines. Similarly, lines I etc. in the 200 line group that is numbers from 200 to 299, inclusive, will be seized by the finders in group B, those finders being the first choice for that group of lines. It will be noted however, that finders'ot both groups A and have ac cess to both groups of lines, so that in the event of any emergency enumerated above, the group I3 finder equipment can serve the A line group as second choice, and the group A finder equipment can serve the I) line group as second choice.

Referring now to the drawings in detail, in Fig. 1, I show a finder switch F which compi s a two-motion switch whose wipers are first moved in a vertical direction to select a level and then 'ioved in a horizontal direction to select a particular contact in that level. The switch mechanism is similar to the well Known Strowger connector switch mechanism, the mechanical details of which are well known to thos skilled in the art and need not be enumerated here in detail. I have provided the finder F with two of wipers.

The one set for seizing lines in the B line group and the other set for seizing lines in the A line group. Permanently connected to the finder I is the selector C terminating in the finder trunk. This selector is of the well known Strowger type in which the wipers are moved in a vertical directionunder the control of the callin device and subsequently moved horizontally under the control of a local testing circuit to seek an idle trunk leading to the next switch of the train. In Fig. 1;, I also show a finder allotter FA which is mechanically similar to the well known rotary llO line switch whose wipers are in no normal position but move in a forward direction only, and whose wipers are advanced by a backacting armature arrangement, that is thewipers are advanced when the magnet of the switch deenergizes rather than when the mag;- net energizes. The finders of" group seen as F for example, are accessible to the control switch through the banks or th finder allottcr FA the allotter serving to connect the finders one at a time to the control mechanism which directs them in search of a calling line. in 1, I show conductors 74, 75, S4, 8 connected to pins bearing similarnumbers with the exponent 1. In 3, I show simarly nun'ihercd pins with tie exponent 2. have made this arrangcmmt to simplify zhe drawings, in practice these conductors will 6 connected thro ,QJh without the use of the s. l V

n Fig; 4, show employed to direct th calling line. The mechanism comprises a seq uence switch SQ which is mechanically similar to the finder allotter F31 and.

I the control 1 echanism which is instrumental in directing the sequence of the operation of the finders F v. .th the'sequence switch in the first position, impulses generated by the impulsing mechanism contained in the control equipment CR are directed to the vertical magnet of the finder, and with the sequence switch SQ} in the second position impulses are directed to the rotary magnet of the finder. W hen thesequence switch moves to its third position at rotary 'impulsing, the finder F is switched through to seize the calling line, the finder allotter FA is stepped ahead one step to associate the control equipment with the next tinder of the group, and the control equipment and sequence switch SQ? are subsequentreturned to normal in readiness for the next call.

In 2 are shown three subscriber stations B. A and A and their ssociated in dividual line equipment throir h which they control the finder equipment when calling. Substation 13 which is designated as No. controls through the relays 201 and 202 the finder group in the normalworlring of the system. The relay 202 energizes IQSPODSPJG to the removal of the receiver from the switchhook in the substation. To start the tinder control mechanism B and to strap ti o hanks of that mechanism sender to direct the tinder its bank. finder such as F to a the termination of the noted that in 2, I show the bani; contacts or" the linoA appearin both in the banks of the finder if and toe uidcr F and that I show normal cables leading oli to the conector hank. 4

In Fig. 3, I show a finder F of the finder group A, connected to a selector S lhe tinder F and the selector S are identical In reality the selectors S and in the same group, their wipers havcess to the same trunk lines. in Fig. also show finder allotter FAG whose u .tions are the same as those of tinder allotter 4 A. It will he noted that the finder allotters FA and Fil have access to all of the finders in both groups, that is, the finder allotter Fr. 1 has access to finders in group A through one-half of this bank, and access to finders in group B through the other hal; Similarly finder allotter FA. has access to both groups of finders. This interconnecting of the finder allot-tors Fil and FA i. made in accordance with one of the objects oi t-ae invention to permitthe control of all of the finders ot' the system by one control equipment, that is, the two groups of finders are thrown into one large group and controlled by one control equipment.

in Fig. 6, I show the control equipn'icnt CR arranged to normally control the finders in group A, this equipment the sequence switch SQ and the relays associated with it. This equipment is a duplicate of the equipment CR shown in 4 and explained above. In Fig. 6, I also show supervisory lamps 611, 612, and 613, which are actuated during the course of operation of the finder groups to apprise the attendant of their workinc; condition.

In Fig. 5, I show marking relays 501 and 502 which are energized to associate the start wire circuit with the control group when acall is initiated in either of the line-groups A or B. Relays 503 and 504isimilarly associate start circuit of the lines in groups A. and B with the control group A responsive to the initiation of a call. In Fig. 5 I also show a two-position manual key which is thrown in one direction or the other to cut out a faulty control equipment and to switch the start circuits so that calls in either group are handled by the one remaining control equipment.

in Fig. 7, i show the rotary stepping control switch ESP) comprising; wipers 05TO'T, which is associated with the control equipment B. This switch is mechanically similar to the sequence switch and finder allotters enumerated above and is stepped in synchronism with the magnets of the finder to count the impulses delivered thereto instrumental and positioning t 1e wipers on the desired bank contact. On the right of Fig. 7 I show a similar rotary stepping control switch RSA comprising wipers 710-712,

which is associated with the control equipment A to perform a similar function. It will be noted that the banks of the two step ping control switches are multipled together. In Fi g. 8, I show, on the left of the figure,

a vertical stepping switch VSB comprising 'ipers 805-809, inclusive, which is associated with the group B control equipment and which is energized simultaneously with the vertical magnet of the finder F to count the impulses delivered thereto instrumental in setting the finder in position to connect with the called line. At the right of the figure I show a vertical stepping control switch VSA comprising wipers 812-860, inclusive, which is associated with the control equipment of group A to perform a sin'iilar function. As in the case of the rotary stepping control switch, the banks of the vertical stepping control switch of group A are multipled to the banks of the vertical stepping control switch of group B for a purpose which will be hereinafter set forth.

Assume for the moment that line 225 initiates a call, and at the moment the linder and control equipment of group A is unoccupied. Responsive to the removal of the receiver from the substation, relay 206 energizes and closes the start wire circuit by the replacing of groundon conductor 257, at ground energizing the register relay 504 to assign the call to the group A finder equipment. Relay 504;

energizes in series with the supervisory relay 608 of the control equipment CR ti o latter relay energizing and closing supervisory circuits which will he enumerated later. Responsive to the closure of relay 504; sender start circuits are prepared by energizing start relay i, which in turn energizing the pulsing relay 607 to complete the pulsing circuit. Relay 607 completes a ci wit to the vertical magnet 31?- of the allotted fin der F energizing that magnet to lift the wipers of the finder F one vertical step. W hen the vertical magnet is completely energized it closes a circuit for the revortive pulse con trol, that circuit extending through the left hand winding of the shunt iiel d stepping control relay 605. Relay (305 is so constructed that it will not operate its armatur. when energized through only one of its windings, and does not energize at this time. The energization of relay 607 also closes a circuit for the motor magnet 810 of he vertical stepping control switch VSA, that magnet energizing in preparation to advancing its *ipers. lVhen the magnet 802 is completely energized, it closes a, circuit for the revcrtive control pulse. that circuit including the right hand winding of the stepping relay (305, since both windings of the relay 605 are now energized the relay attracts its armature and opens the above circuit to the vertical magnet of the finder F and to the nt ultiple mag net of the vertical stepping control switch VSA, permittiiig those magnets to deener-,

gize, the former dropping back preparatory to taking in an additional step, and the latter dropping back to advance the switch wipers The energization of relay 206 closes circuitsv closed through the wipers of the vertical stepping control switch so that when the relay 005 again closes the above enumerated c1r- 'cuit it closes an additional circuit to the iagnet 610 of the sequence switch SQ Relay 605 energized in the above explained manner to terminate the pulse, a vertical magnet of finder F and the motor magnet of the vertical stepping control VSA energizing as before. Magnet 610 of the sequence switch SQ being also energized, deenergizes upon the energization of relay 00 5, and advances the sequence switch wipers 653 to 655, inclusive, one step. lVhen the magnets have all deenergized, wipers of the finder F are standing opposite the second level of banks, wipers of the sequence switch SQ, are in the second position, and the wipers of the vertical stepping control are standing on the second bank contact. lVhen the relay 605 deenergizes it again closes the pulsating circuit which is now directed to the rotary magnet 313 of the finder F and to the motor magnet 7 02 of the rotary stepping control switch RSA, comprising wipers 710 to 712, inclusive, those magnets energizing to advance the finder allotter wipers one step and to count off the impulses delivered thereto. Vhen both therotary magnet and the motor n'lagnet of the stepping control switch are fully energized, relay 605 is again energized by the revertive pulses to permit the magnets to restore to their normal position.

From the foregoing description it will be apparent that the interval between the vertical and rotarv impulse transmission is no longer than the interval between successive vertical. impulses. As the vertical magnet is being operated to elevate the shaft and g the latter are set to vibrating. that on attaining considerable amplitude .ine ninth or tenth. It is impossible to rolate the wipers into the selected level while i v are vibrating and therefore I have a d the shaft so that two rotary steps are ary to bring the wiper into engagement with the first contact in the bank levels, The

quence switch SQ}.

time required for this extra rotary step when added to interval between impulses is sulficient to permit the wipers to come to stop vibrating, so that when they are moved into the level they will properly engage the contacts. 7

Returning new to the call'in progress, since the calling line is No. 25, etc. six rotary steps will be necessary, the magnet and stepping relay 605 working together in the above manner advance the wipers to the fourth bank position. At this time a circuit is closed through springs of relay so that when the impulse is delivered to the magnet it is also delivered to the magnet 610 of the so- That magnet energizes preparatory to advancing the wipers of the switch into the next position. At the completion of the sixth pulse the wipers of the tinder F are standing on the fifth bank contact set which leads to the calling line A When the sequence switch SQ} positions its wipers in the third position it prepares the switching through circuit which is closed as soon as the relay 605 restores, that circuit energizing the relay 306 to connect the finder F with the calling line. The energization of relay 306 closes the calling loop circuit to the line relay 305 of the selector S energizing that relay preparatory'to subsequent control by the calling subscriber. Relay 306 also closes a circuit for the relay 203 or the line relay group associated with the calling line, that relay energizing to disconnect the relay to permit it to restore to normal. The

closing of the switch through circuit completes the functions formed by the control group and setting the finder switch F on the contacts of the calling line, that equipment restoring to normal in readiness for the next call. 7 r

\Vhen relay of the control group CR was energized, it closes a circuit for the relay 602 which energizes and locks itself to the upper winding of the relay 601. Relay 60? also closes the circuit through the lower winding of the relay 601 which energizes and switches the start circuits of the remaining Hues in group A so that in the event one of hose lines should call while the equipment 11 is occupied it would be handled by equipment SR which will he explained presently. Relay 007 also closes a circuit for the magnet 31% or" the finder allotter F A energizing that magnetpreparatory to advancing the wipers to the next step. When the finder F is switched through to the calling line, the circuit or relay007 is opened permitting that relay tor store and open the, circuit of magnet- 31 jl, which deenergizes and advances the wipers to the next set 01 contacts which leads to another finder such as F The finder allotter F A remains on the next contact set if a finder associated therewith is idle, and steps oil of that contact set it the finder associated therewith is busy searching. under the control of a local circuit for the first idle finder in the group. Relay 602 being locked in series with the upper winding of relay 601 holds the two relays in an energized position after relay 607 deenergizes. -When the completion of the switch through operation the circuits are closed for the mo tor magnets of the vertical and rotary stepping control switches, under the control of a local interrupting contact, which causes the magnets of those switches to act in a buzzer like manner to advance the wipers to their normal position. When the wiper 712 and 812 of therotary and vertical stepping control switches, respectively, reach the next to the normal position, they close a circuit 'hrough the lower winding 01 the relay 602 and the motor magnet 702 and 802, these magnets cin in parallel in the circuit. Relay 602 is dinei-entially wound and the lower rinding is so proportioned that when the W0 n'iaguets are energized in parallel through it, the flux it produces neutralizes the flux of the upper winding and permits the relay to deenergize. The deenergization of relay 602 unlocks relay 601, thereby restoring the control equipment CR to normal in readiness for the nextcall.-

A call originating in sub-station B, which is in the 200 line group which is normally served by the control and finder group B energizes the relay 202 throwing the ground on the start conductor 256 to energize the register relay 501 in series with the supervisory relay l02. The energization of relay 501 closes a circuit for start relay 406 which ener gizes to start the finder control equipment CR in search of the calling line. Relay .lOG closes the circuit for relay 103 which energizes and delivers impulses to the vertical magnet of the finder F and to the motor magnet 01 the vertical stepping control switch VSB to step and control the vertical motion of the wipers of the finder F in the above describedmanner. Shunt field relay energizes to terminate the pulse before described, in connection with CR Belay 202 closes a circuit so that when the second pulse is delivered to the magnets 01' the counting switch and vertical magnet oi the finder, a circuit is also completed for the magnet of the sequence switch SQF, energizing that magnet preparatory to advancing the wipers to shift the circuit from the \"ertical magnet and control to the rotary magnet and control. At the termination of the second-impulse the sequence switch is advanced andthe wipers of I are standing opposite the second level of the bank in readiness to be rotated into that level to the contacts of the calling line. When relay 05 again de energizes the next impulse is sent to the rotary magnetthereto and to the magnet of the rotary stepping control swltch RSB to advance the wipers F and RSB, finally bringing the wipers F to rest on the bank contacts of the desired line. The motor magnet no of the sequence switch is also energized in multiple with the rotary magnet on the last impulse over a. circuit completed through the energized relay 202. When the relay 4.05 energizes after the lastimpulse, the sequence Bola 1 404: com aletes the circuit for switchim Q relay 409, which energizes and opens the circuit of start relay 406 preparatory to to storing the control mechanism to normal. Relay d04- also closes a circuit through the upper winding of relay e08 energizing that relay which locks itself through the upper winding of relay to control the returning of the counting switches to normal in readiness tor the next call.

Returning now to the operation of the findor control group equipment A while connect- .ing with the line 225, and assuming that after the station A initiated a call and before the finder F connected with the line, subscriber at station A removes his receiver preparatory to making a call. Under these conditions the subscriber at station A will be delayed slightly in making this call, because no finder equipment is available at the instant and consequently his line will not be connected with the first selector immediately. Tl e delay however is momentary existing only until the control equipment sequence switch SQ moves into the third or switch through position. At this time the locking circuit of register relay 504 is opened, the switching relay (S0l is energized, so that the suit wire circuit grounded by the energization of relay 20 i is completed through to the relay 502, energizing that relay to register the call in the group B equipment. The equipment CR is ready to immediately start a finder such as F in arch of the calling line through the second choice or A set of wipers. The energization of relay 502 closes a circuit for the wiper switching relay 7 of the finder F onergizing that relay so that when the wipers are positioned on the bank contact the finder will be connected through to the line A It will be noted that the group B equipment picks up the overflow calls in the group A before the group A equipment has completed its cy 1e of operation in connecting with the first line calling. As soon as the sequence switch SQ has moved into the switch through position, the start circuit to the group B equipment is completed so that equipment may befunctioning while thecontrol equipment CR is restoring to normal while the finder allotter FA is preselecting the next finder to be used.

Similarly it while a call from line 225 is being "found by the group B finder equipment, a call is originated by a second line in the B line group, that call will be handled. by the group A finder equipment through the second choice or 13 set wipers as soon sequence switch SQ has moved into the switch through position, at which time relay 409 will energize, relay 501 will deenorgize to switch through the start circuit so'that the ground placed on the start wiper by li"-e relay such as 202 will energize the register rclay to register the group 13 call in the group A finder equipment. The energization oi relay 503 closes a circuit for the wiper switching rel y 307 of the tinder 1*, which energizes and connects the second choice wipers 270 to 272 so that when the wiper sets are positioned on the bank contacts, the finder F will be connected to the calling line in the B group.

In the foregoing general explanation of the workings of the system of my invention, 1 have assumed that the equipment was tune tioning properly. Assume now that some mechanical or electrical tt'ault exists, and that the vertical magnet of the finder F fails to return. the revertive pulse to terminate the impulse delivered to it by the control equipment CR It will be noted that the energization of relay prepares a circuit for the slow to pull up relay 606, and the circuit being under the control of springs 637 of the shunt field stepping relay 005. This shunt field relay will not operate unless both ot its l 9.8 .ie

windings are energized, the circuit through springs 637 is not interrupted and the slowto-pull-up relay 000 energizes alter a brief interval. The energization of this relay completes a circuit tor the switching relay 601 and unlocks the startrelay 00 i. Register relay 50-1 will doencrg ze after a brie inteiw'al and the start circuit ground over which relay 50: was initially energized will he led it vcr a circuit through the worl contacts on the switching relay 001 to tl wimling of relay 502 of the group B eqmpment so that the call ill be picked up by that equipment. The encrgization of relay 006 also completes he release circuits of the finder group A,

and instructs the finder allotter Fr l oti of the contacts leading to the faulty finder. In this case of trouble no supervision would be given to the stationattendant, as the trouble is not very serious, merely throwing out oi service :the one finder F Y Assume for an ins ant that the motor magnet 802 of the vertical stepping switch was burned out and that svitcn could not be stepped to count the pulses delivered to the vertical magnet ot the finder.- The mag grounded springs 333 of the finder the other finder of the group in multiple. As

net 802 would therefore not return its re vert-iv'e pulse to thewright hand winding of relay 605 and the slow-to-pull-up relay 606 would be energized to transfer the call to the group B equipment in the manner explained above. Relay 606 would. again close the circuits for returning the equipment to normal and since the magnet 802 is burned out that switch would not return to its normal position, consequentl the control equipment CR would not be released and after an interval a nal would be brought up to notify the attendant that the control equipn'ient was tied and out of service. Calls coming into this system duringthis interval would be handled by the control equipment CR and the finders of the group ll.

' A burned out magnet such as mentioned above would disable the control equipment CR for a relatively long period of time during which renairs were being made. The attendant upon noting the signal that the control equipment CH is out of service will operate the key K to cut the control equipment CR permanently out of service, and divert the start circuit from both the A and B groups of subscribers lines to the B control equipment so that all calls from both groups are handled by the one equipment. The operation or". the key K lso completes circuits so that the control equipment Cl can control the finders of the A group as well as the finders ot the B group which are normally controlled by it. It will be noted that in the banks of the finder allotter FA the contacts of the first half of the banks lead to the finders'in the B group, and that the ontact-s in the second half of the bank lead to the finders in the A group. When the key is operated to cut-out one o1 the control equipments the finder allotter such FA? searches for an idle find er in both the it and B groups. Thus it will seen that in case of emergency the operation of the key l; throws the two groups of finders into one la ge group which is controlled by the remain control equipment.

Similarly it the control equipment CR becomes detective the si given to 'nal will be I the attendant and he. will operate ti o key K in the opposite direction by transferring the start circuits from the B group over to the A control equipment and throwing the two groups of finders together sothat finder allotter FA will have access to the ntire number of finders. V

In the control equipment CR is an all finder busy relay 603 which is normally energized over a circuit completed through the F and long asthere remains one idle finder in he group A, relay 603 will be energized. but when the last idle finder in the group is op erated, the relay 603 deenergizes and coinpletes a circuit for'the switchingrelay 601 'blown out by an over load, the relay 603 will deenergize and close a circuit for relay {301 which with its separate fuse will not be atfected by the blown main ruse and will energize tov transfer the call to the group ll. Group B is of course similarly equipped, the constantly energized relay being relay 407 which is used in common with the equipment CR and the switching relay 409 is provided with a separate luse as shown.

In order to gi o satisfactory service of a more or less special nature, such as toll service, it isnecessary that the subscribers lines be classified into certain groups, and that the toll recording operator be informed as to the group to which the calling line belongs. T hen a system such as I have described in the presentinvention, discriminating tones can be readily given to the recording operator over the release or holding trunk in the usual manner. As shown in Fig. 2 the finder bank contacts appear in the same relative position as the connector bank contacts, that is, line B which is assun'ied to be No. 225 appears in the twenty-fifth bank posit-ion of the 200 line finder group as well as in the twentyfifth position ot-the 200 line connector group. The drawings are so shown merely to avoid unnecessary complication, and it will be readily appreciated that by the introduction of a distributing frame between the subscribers line and the finder equipment, the subscribers line can be connected to the finder equipment as the occasion demands without any regard to the connector bank numbers of the line. that is, the directory listing of the line. In the embodiment of this idea I propose to group all of the subscriber's lines having a certain class of toll service allowed to them in the B group and all of the lines having a different class of service allowed to them in the A group. and have arranged the tone accordingly. Referring now to Fig. 1 it will be noted that tone one is normally connected to the rerelease trunk conductor 68 through the normal contacts of the switching relay 7 and the make contacts of the switch through relay 6. The tone number one wbe picked up by the toll recording operator to ascertain the class of service allowed to the calling subscriber. It for some reason the subsc iber at station E is reclassified as regards to toll service, his finder bank number might be changed to 125 or any other number in the 100 group, by simply lilting the jumpers and transferring them to the aslease magnet circuit of the finder i signed number. In that case the subscribinat- B upon n'iaking the call would be connected to the finder F through the other 'et 0t wipers under the control of the energization of relay 7. Relay 7 energizes and connects the tone No. 2 through the springs d5 of the switching relay 6 to the release conductor 68, to inform the toll recording operator tl it the subscriber is entitled to the class of service 1 ated by tone 2.

Having thus described my invention in general I will now proceed with a detailed description ot its operation. Assume that the subscriber at station A whose finder bank number 125 initiates a call. When the receiver R is moved from the hook switch H a circuit is closed for the relay 204:, traceable from ground on sprin s 219 through the hook switch, receiver, tran iti'cr and calling device oi? the substation it throrgh springs 218 through the windi no, of relay (ll to grounded l attery, energizing the relay to initiate the call. The energization of relay 20% at springs 217 puts the round on the start wire conductor to energize the start rixay in the finder control group to be used in pic f up the call. Assume for the moment that group (ll-l is idle at the moment,

in which case it will be operated to pick up the cal since it is the first choice oi the group A, which cont us the calling line A Accordingly Q closes a circuit for the register relay and the SUPQH iry relay 608 of the control erpupinent CR that circuit being traceable from grouno and spring 213', conductor 257, through springs 54st, conductor 585, through springs 520,. conductor 562, through spring 621 and its break contact, conductor 563, through springs 536,, through the winding of relay to conductor through the windi of relay 608 to grounded battery. Relays l and GOS energze over this circuit, the latter to open at springs 641% the reprevent its operation at this time and to close at springs6-l-., a circuit through the supervisory lamp 613 to indicate that the control equip respective break contact in multiple to con ductor 566, through springs 54b3, through relays 504; and 608 tobattery. Relay 604- is short circintcd by the start conuuctor ground on spring 5%, until relay 504i is fully one"- 'ized to break the start circuit at springs 5%. Relay iT then energizes. Relay 60% upon energizing closes at spring 633, 634;, and 635 and their respective make contacts, circuits which will be explained in detail hereinaft r.

Relay 604 also closes at springs 636 a circuit for the relay 607, the latter relay energizing to start the finder control equipment in operatiou. The energization of relay 607 closes'at springs Gl-Jl a circuit through springs 637 and the upper winding of slow operating relay 606 through grounded battery. In the normal operation of the system, however, relay 606 does not energize at this time because itscircult opened at springs 687 by the operation 7 The first cortical impulse.

The operation of spring 647 closes a circuit from ground through springs 64?, springs 639, through the wiper 654 of the sequence switch SQ, that Wiper now being in engagement with the first bank contact or with the bank contact lnultipled thereto, conductor 662, through Wiper of the finder allotter Fil that wiper now being in engagement with the first bank contact leading to the finder F conductor 356, tl'irough the winding of the Vertical magnet 312 to grounded battery, energizing the vertical magnet to elevate the shaft carrying the wiper groups A and B through one vertical step. The operation of the vertical magnet produces other changes in the finder F which will be explained in detail later. The opera tion of spring 646 of relay 604 closes a cir cuit from ground through springs 6 l6. spring 638, through wiper 655 of the sequence switch SQ}, that wiper also being in engagement with the first bank contact or a con-- tact Inultipled thereto, conductor 578 through the winding of the magnet 802 of the switch VSA to grounded battery. The ground on conductor 578 is also conducted through springs 54? to conductor 582, this latter circuit being without effect at this time. The operation of magnet of the finder F closes a circuit from ground through springs 530 to the conductor 360, spring 52S and its break contact, conductor 564, thence over two paths in parallel'one through the resistance 614 to grounded battery, and the other through the right hand Windingof rclay 605 to grounded battery, energizing the relay 605. The relay 605 being of the-shunt field type does not operate its armature when energized through only one of its two windings, so the energization of relay 605 as c plained above is without eftrzt unless the other winding is energized. "llheoperat'ion ol the magnet 802 of VSA closes a circuit from ground through springs 811, conductor 5'75. 1

(ill

now energizes, both of its windings are energized, and operates its armatures to open springs 637, 638, and 639. The operation of springs 637 at this time prevents the energization of relay 606 as indicated above for a purpose which will be detailed hereinafter. The operation of springs 638opens the circuit of the magnet 802 which as traced thereto, permitting that magnet to deenergize and advance the wipers 812 to 916 of the switch VSA one step, and to remove the ground from the circuit of the right hand winding of relay 605 at spring 811. The operation of spring 639 opens the circuit of the vertical magnet 312 which was traced thereto, permitting the vertical magnet to drop up in readiness for the neXt pulse, and to remove at spring 330 the ground from the circuit of the left hand Winding of relay 605. The two windings of relay 605 are made slow to deenergize by the shunting of the windings through the resistances 614 and 615, respectively to battery, thereby causing 1'elay 605 to remain in its energized position sufficiently long to hold the circuit of the above magnets open long enough to permit the armatures to restore to normal and perform the functions indicated. By adjustment of the value of resistances 614 and 615 the pulse ratio delivered to the magnet can be varied to suit the requirements of the switch structures controlled thereby.

The Zast oertz'cal impulse.

Since the calling station A has the finder bank number 125, its bank contacts appear in the second level of the 100 group, and consequently two vertical impulses are all that are required to elevate the wipers of the finder F in position to subsequently connect with the line contacts. If some other number were calling the foregoing impulsing would continue to elevate the wipers opposite the level containing the contacts of the calling line, the operation being exactly as detailed above and need not be repeated. Returning now to the present call when the magnet 605 deenergizes at springs 638 and m,

302 and 312, respectively, energizing thosemagnets as before. Since the'contacts of the calling line arein the second bank level, the the ground placed on the conductor 578 by the springs 638 traverses a circuit through the springs 5&8, conductor 582, through the tenth A common of group A, conductor 260, through springs 215 of the line relay 20st to conductor 261, through the second A common of group A, wiper 814 now engaging the second contact in its bank, conductor 584, through springs 545 to conductor 576 through the first contact in the bank of SQ}, through wiper 653 which are in engagement therewith, through the winding of magnet 610 to grounded battery energizing themagnet 610 not) it again closes the circuits for magnet preparatory to advancing the wipers 653-655, inclusive, of the sequence switch SC? to the next bank contact. VJhen the relay 605 is then energized responsive to the complete operation of magnet 312 and 802, at springs 638 and 639 it again opens the circuit of mag net 802 and 312 and in addition opens a circuit just traced for the magnet 610, permit ting these three magnets to deenergizc the former performing the same functions as before and the latter advanc' 1g the wipers and 655 of the sequence switch SQ} into the second position from which it controls subsequent impulses, directing them to the rotary magnet 313 of the finder F and to the magnet 702 of the rotary stepping control switch EPA as will now be explained.

The first rotary impulse.

Since SQ} has been acvanced to the second step, the circuits for the vertical magnet and the vertical stepping control are opened and when the relay 605 falls back after a brief interval it closes a circuit for the rotary magnet 313 and the rotary stepping control switch BSA. The rotary circuit being traced from ground on springs 647, through spring 639 and its break con tact, wiper 65d of SQ the second bank or the contacts multipled thereto, via conductor 661 through the wiper 354 of FA through the Winding of the rotary magnet 313 to grounded battery, energizing that magnet to rotate the wipers one step and to close at springs 325 a circuit for placing ground on conductor 360 to energize the left hand winding of the relay 605 as before. The circuit for the magnet 702 of the switch BSA is closed from ground on springs 646, through spring 638 and its break contact, wiper 655 of SQ engaging its second banks contact or a. contact multipled thereto, conductor 577. through the winding of magnet 702 to grounded battery, and a multiple circuit through springs 546, to conductor the latter circuit being open is without effect at this time. Magnet 702 energizes and prepares to advance the wipers 710 and 712. inclusive, of the switch BSA one step, and at spring 709 closes a circuit from round to conductor 575 to energize the i ght hand Winding of relay 605 hereinbefore es:- plained. Relay 605 energizes and opens the above traced circuits to end the pulse, the magnet 702 falling to advance its wipers and the magnets 313 falling back preparatory to taking another step. Thus it will be seen that the rotary magnet receives an impulse immediately after the last vertical impulse, the interval between being no longer than the interval between successive vertical impulses. Because of the speed at which the wiper shaft of the finder F is traveling itis necessary that the wipers be spaced two steps off the banks, that is the rotary magnet must receive Ill till

two impulses before the wipers engage the first bank contacts. This arrangement is necessary because the wipers in their vertical movement are set to vibrating and if they are cut into the bank level on the first rotary pulse while still vibrating they frequently will not properly engage the contacts of the level. Since the calling line has a finder bank number 25 its bank contacts will appear as the fifth set in the second level, and consequently the rotary magnet must be energized six times to set the wipers on its contacts. The foregoing operation of the rotary magnet and the rotary stepping control magnet continues for five impulses, the relay 605 energizing to terminate each impulse.

Last rotary impulse.

WVhen the magnet 7 02 deenergizes after the fifth impulse to advance the wiper 710-712 onto their fifth bank contacts, the miltiple circuit from the grounded conductor 577 through the springs 546 to the conductor 583 is completed through the wiper 81.3 of VSA now in engagement with thesecond contact of its bank over the second B common of group A to the conductor 259, through springs 216 of the line relay, to the conductor 258 which is connected to the fifth C common of the group A, wiper 711 now in engagement with its fifth bank contact, conductor 581, through springs 548, conductor 579, through the second bank contact of SQ through wiper 653 to the winding of magnet 610 to grounded battery, energizing the magnet 610 preparatory to advancing the sequence switch wipers one step with the end of the pulse.

0R switches through.

WVhen the relay 605 again energizes to end the impulse, magnets 313, 702 and 610 fall back, the former to performing the same functions as before and the latter advancing the wipers of the sequence switch SQ into their third position. \Vith the sequence switch in the third position the circuits to the magnet, of the finder F and the stepping control switch RSA are no longer closed, and as a consequence, relay 605 remains deenergized long enough to permit the energization of relay 606 over a circuit traceable from ground through springs 644, spring 637 through the upper winding of the relay to battery. Relay 606 upon energizing closes a circuit from ground on spring 645, through spring 640 thence over two parallel branches, the one through the lower winding of relay 601 to battery, and the other over conductor 668, through spring 632 and its break contact, conductor 566, through the winding of magnet 314 of the finder allotter F11 to grounded battery, energizing the relay 601 and the magnet 314. Relay 606 also closes a circuit from ground through springs 647, springs 639, springs 641, conductor 652 through springs 625 through the upper winding of relay 602, conducto 568, through the winding of relay 608 to battery, energizing the relay 602 whichcloses a locking circuit for itself through the relay 601, that circuit being traceable from ground through the up per relay 601, spring 625 and its make contact, through the upper winding of relay 602 thence over the previously traced circuit through relay 608 to battery. It should be noted that the advance of the sequence switch wipers to the third position closes a multiple circuit around the contacts 641 in the circuit just traced for the relay 602, that circuit being closed slightly before relay 606'pulls up, to insure that relay 602 will energize first. The energization of relay 601 operates the springs 623 and 624 to open the circuitof relay 604, that relay being slow to release does not fall back at the instant but remains in its energized position for an interval sufliciently long to permit the completion of the switch through function of the finder F as will be explained presently. The operation of springs 623 and 624 closes a locking circuit for the relay 504 which is traceable from ground through spring 634 and its make contact, conductor 673, spring 624 and its make contact, conductor 566 through springs 543 through the winding of relay 504 and thence over the previously traced circuit through relay 608 to grounded battery. The operation of springs 623 closes a switch through circuit from the ground just traced to spring 624 and its make contact, through spring 623 and its make contact, conductor 667, springs 643, conductor 663, through the wiper 351 of FA now in engagement with the first bank contact, through conductor 358, through the winding of relay 306 through resistance 315 to grounded battery, energizing the relay 306' to perform functions that will be explained in detail presently. The positioning of the wipers of sequence switch SQ, in their third position closes a circuit from ground through spring 646 and its make contact through the third position of the bank of SQ through the wiper 653, through the winding of magnet 610 to grounded battery, energizing the magnet preparatory to advancing the switch wipers to the next bank contact set. The circuit of relay 604 having been opened as explained above, the relay falls back after an interval and closes a circuit from groundthrough spring 634 and its break contact, conductor 669, through springs 629, conduct-or 574, through springs 708 and the magnet 702 of BSA to grounded battery, energizing the magnet 7 02 which interrupts its own circuit at springs 7 08, and falls back to advance the wipers 710 to 712 of the switch BSA one step. The magnet 7 02 operates in a buzzer like fashion to advance the wipers until the wiper 712 engaged the contacts 712, at which time a circuit is closed from ground through the lower winding of relay 602, through spring 626 and its make contact, conductor 580, through the wiper 712 of BSA, contact 712, conductor 577, through the winding of magnet 702 to grounded battery, holdingthe magnet energized independent of the contacts 708.

7 Relay 602 is differentially wound and has its lower winding so proportioned that the flux set up therein by the current flowing over the circuit just traced is not sufiicient to counteract the flux set up by the current flowing through the upper winding of the relay, consequently the relay remains in an energized position at this time. The deenergization of relay (504 also closes a circuit from ground, through spring 63% and its break contact, conductor 669 through springs 628, conductor 560, through springs 810 and the magnet 802 of VSA to grounded battery, energizing that magnet which interrupts to its own circuit at the springs S10 and operates in a buzzer like fashion to advance the wipers 812 to 816, inclusive, forward until the wiper 812 encounters the contact 812. A circuit is now closed from ground through the lower winding of relay 602, through springs 62?, conductor 569 through the wiper 812, through the magnet 802 of VSA to grounded battery, holding the magnet 802 energized independ entof the springs 810. The current flowing through the lower winding of relay 602 is thus increased by the amount of current flowing through the magnet 810, and the fiuxset up in the lower winding by the combined currents oi the magnets S02 and 7 02 is sufficient to counteract the flux set up by the upper winding of the relay, with the result that the relay 602 deenergizes, unlocking the relay 601 permitting that relay to deenergize and thereby restore the control equipment SR to normal in readiness for the next call. Returning now to the deenergization or relay 604, when spring 634 falls back away from its make contact, it removes the ground from conductor 673 through which conductor relay 504 was locked, permitting that relay to deenergize and close the group A start -cir cuit so that if another call should be waiting at the instant, that start circuit will be closed through to relay 501 of the group B control equipment which willhandle the call in the manner explained hereinafter. The energization of relay 604 at springs 636 opens the circuit of relay 697 which falls back and at springs 6 15, 646 and 647 opens the circuit of the sequence switch magnet 610 and the finder allotter magnet 31%, permitting those mag nets to deenergize and advance their respective wipers to the next contact seti FA searches for idle fi mZc-r.

The deenergization of magnet 314 advances the wipers of the find-er FA onto the next bank contact set, for the purpose of illustration it will be assumed that that contact illl set is the set leading to the finder F and that at the instant the finder F is busy. A circuit may then be traced from ground on spring 332, the ofi'-normal assembly of the finder F and its make contact, conductor 35?, first bank contact and the iper 852 of FA conductor 671, spring 633 and its break contact, spring 6-30 and its make contact, conductor 665, through the spring 350, through the winding of the magnet 31% to grounded battery, energizing the magnet, which interrupts its own circuit at springs 3:30 and falls back to advancethe wipers one step. if the next finder in the group is busy the bank contact engaged by the wiper 352 will also be rounded and the circuit for magnet 31% will again be completed, tl at magnet energizing as before to advance the wipers another step. In this manner the finder allotter searches for the first idle finder in the group, at which time the above circuit for magnet 314 will not be completed and the finder will come to rest on the contacts leading to ha finder.

Operation of finder F set of contacts in the second level of tho tinder banks. It will be noted that the wipers 27 to 275, inclusive, comprising the A group wipers are connected to the hr ak contacts on the relay 30?, those wipers being used when the finder F is actuated respons ve to the initiation of a call in the A line 9 up. Similarly the wipers 270 to 272, lIlClUSl\ e, comprising the group B wipers are connected to the make contacts through the relay 30?, those wipers being used when the finder F is used responsive to the initiation of a call in the group B line as will be explained in de tail hereinafter. When the vertical magnet energizes responsive to the first impulse it elevates the shaft containing the wiper sets A and B one vertical step operating the otl normal spring GYS, which at springs 331 opens the circuitof relay 603 ot the control equipment CR for a purpose which will be explained hereinafter, and at spri g 331 and its make contact, prepares a on uittor the release magnet 311, that circuit being held open elsewhere at the time, the release magnet does not energize. The operation of springs 332 of the oil-normal assembly OHS opens a point in the circuit of the wiper switching relay 807, preventing the energization of that relay at this time, Vfhen the control equipment CR switches through as explained hereinbei ore, and energizes the relay 306, that r lay operates springs 32?, 328, and 829 to connect the calling line A to the line relay of the selector S over a circuit traceable from ground through the low-' er winding of relay 305 of the selector S spring and its break contact, conductor 360, springs 329, spring 324 and its break contact, conductor 375, wiper 281, now engaging the plus terminal of contacts sets 125 of the A bank group, through conductor 248, through the hook switch, receiver, trans initter, and calling device oi the calling station A to the negative line conductor 240 to the wi per 270, conductor 273, spring 322 and its break contact, spring 327 and make contact, conductor 350, through spring 342 and its break contact,-through the upper winding of relay 305 to grounded battery, energizing the relay 305. At springs 2344, relay 305 closes a circuit from ground on springs 345, spring and its make contact, through the winding of relay 304 to grounded battery. Relay 304 energizes and at springs 335 places ground on'the release trunk conductor 358 which traverses the winding 01 relay 306 to resistance 315 to battery, holding the relay 306 in its energized position. Relay 306 which was energized initially over a circuit under the control, make springs on relay 604 must switch through and close the circuit of relay 305 quick enough to permit that relay to energize relay 304 to return the holding ground before the relay 00-iof the control equipment CR deenergizes. The energization of relay 306 closes a circuit from ground through spring and its make contact, through spring 328 and its make contact, spring 323 and its break contact, conductor 274, wiper 280 now engaging the private contact ot' the twenty-fifth bank set of group A, conductor 247 through the winding of relay 203 to grounded battery, energizing the relay 203 which at springs 218 and 219 removes the relay 204 and the ground connection from the conductors of the calling line, leaving that line connected through to the line relay of the selector S with all bridges detached.

A dial tone source is interposed between the lower winding of relay 305 and ground in the usual n'ianner. This source is omitted from the drawings to avoid unnecessary complication. The subscriber on hearing this dial tone knows that the central ollice equipment is in readiness to handle his call. The calling subscriber may then. operate the selector S" by a manipulation of his calling device Cl), to step the wipers 341 to 349, inclusive, to the desired level, from which point the operation of selector S is automatically performed to'select an idle trunk in the selected group. The operation of the selector S is well known to those skilled in the art and need not be repeated in detail at this time.

Releasing F As the subscriber proceeds with the setting ot his call, conductor 358 is extended through springs 343, wiper 348 etc, that conductor being maintained grounded by the release relays of the switches employed, through springs similar to When the conversation is completed and the subscribers have hung up their receivers, ground is removed from conductor 358 in the manner well known. to those skilled in the art. telay 306 which is held energized by ground on conductor 358, deenergizes, and at the normally closed contacts controlled by spring 328, prepares a point in the circuit of release magnet 311. If GR is idle at the moment the circuit of magnet 311 will be closed from ground through spring 333 and its break contact, normally closed contacts controlled by spring 328, spring 331 and its make contact, winding of magnet 311, conductor 664, through springs 348, through the winding of relay 609 to battery. Magnet 311 and relay 609 energize over this circuit, the former to release the switch F and the latter to close the obvious circuit for supervisory lamps 611 and 612. When the shaft of F returns to normal, oil normal springs 33 1 and 332 are moved to their normal positions, the former to open the circuit of 311 and 609 and to reclose a point in the circuit of relay 603. Spring 332 in its normal position closes a point in the circuit of wiper switching relay 307 for a purpose which will be explained in detail hereinafter.

It CR is in use when relay 306 is deenergized, the circuit for magnet 311 and relay 609 will be held open at springs 348 of relay 608. The finder F will not be released until CR restores to normal to permit relay 608 to deenergize.

Line B calling through group B equipment.

Having thus completely traced the circuits involved in a call through equipment of the A group when a group A line is calling I will now proceed with the description of a call from the B group when the call is handled by the group B equipment comprising the finder F and the control equipment CR \Vhen a subscriber at B removes his receiver to initiate a call the line relay 202 energizes over a circuit including springs 213, the calling line, and the instrumentalities at the substation. Assume that at the instant relay 202 energizes, the control equipment CR is idle and in readiness to handle the call. A circuit will then be completed lt'rom ground. and springs 212 over conductor 256 through springs 513, over conductor 587, through springs 537, conductor 456 through spring 435 and its break contact, conductor 453, through springs 519 through the winding of relay 501, over conductor 550 through the Winding of relay 402 to grounded battery, energizing the relay 402 and the relays 501. The former relay opens atits springs 431 a point in the release magnet circuit of the finder F and the latter registers the finder ion 

